Wear gloves, an N95 or better respirator, and eye protection
Ventilate the area
Stop and fix the moisture source first
Remove and discard any sheetrock that is soft, crumbling, or heavily moldy
Cut out damaged drywall at least 12 inches beyond visible mold if needed
Bag contaminated material before carrying it through the house
Clean remaining framing and nearby surfaces with detergent and water
Use a mold-killing product approved for the surface, following the label
Dry the area completely with fans and dehumidifiers
Replace removed sheetrock only after the area is fully dry
Prime and paint with mold-resistant products if appropriate
Clean or replace insulation, baseboards, and other affected materials
Dispose of contaminated PPE and cleanup materials properly
Call a professional if the mold covers a large area or keeps returning